Tweco 300 XT Auto-Cut 400V - Manual (Page 133)

AUTO-CUT 300 XT
Manual 0-5290 APPENDIX A-51
Relay PCB
• Relay board LED D12, Work Current Detected, will light if the current sensor signal exceeds 0.05V. If
D12 is on, measure the sensor output signal at J1-3 with signal common on J1-1. This signal should be
0V +/- 0.04VDC. If greater than +/- 0.04VDC with no work lead current, the sensor is defective. If the
signal voltage is within the limits and D12 is on, then the Relay board is defective.
• If D12 is not on and the 207 code is still active, either the Relay board or the CCM is defective.
CCM or ribbon cable
• The work current signal leaving the relay board is on the 40 pin ribbon cable (Relay J4 to CCM J23) pins
27 (-) & 28 (+). If the voltage here exceeds 0.1VDC with no work current the Relay board is likely defec-
tive. Another possibility is in the 40 pin ribbon cable either pin 27 or 28 is shorted to an adjacent pin.
Otherwise the CCM is defective.
2. 207 code after START applied (during preflow):
• Short between power supply negative output and Work circuit.
• Short between power supply negative output and earth ground.
• Defective or incorrectly installed user supplied equipment such as torch height controls that make con-
nections to power supply output.
Shorts are more likely to cause DC output voltage low (code 205). However, if the short has enough resistance
it is possible to show code 207. To test, remove negative output cable and reapply Start. If 207 code does not
appear problem is a short somewhere outside the power supply.
User Installed Equipment
For user installed equipment to cause 207 code it would have to be connected on the output (to the rear) of the
current sensors. To test, disconnect user equipment and apply CNC START. If code 207 is gone user equipment
was defective or connected incorrectly.
208 Unexpected current in Pilot Circuit
The Pilot board includes a current sensor to measure the pilot current. There should not be any pilot current
until the inverters and the pilot board are enabled and the arc starter has fired to ignite the pilot. Pilot current
or the signal indicating pilot current should not be present until the arc starter has fired.
Unwanted current signal due to defective sensor or defective circuit boards will most likely be present as soon
as the power up sequence completes and will be indicated as an active fault, E208. An actual short allowing
real current to flow in the pilot circuit will not occur until the inverter and pilot board are enabled near the end
of preflow. This will result in the inverters immediately being shut off and displaying a “last” or “latched”
fault, L208. An LED, D2, on the Pilot board lights when the Pilot Board is enabled.
1. 208 code before START applied:
• Defective Pilot board (current sensor circuit).
• Defective Relay PCB
• Defective CCM
Pilot PCB
Pilot current signal is on the 10 pin ribbon cable (Pilot J42, Relay PCB J3) between pins 8 (-) and 9 (+). With no
current, the signal should be zero +/- 0.05 V. Also the Relay board has an LED, D11, “Pilot Current Detected”,
which will light if the pilot current signal exceeds 0.15V. If the signal is not zero V.Pilot PCB is likely the cause.
To be sure, disconnect the Pilot board ribbon cable from the Relay board at J3. If D11 goes out, the Pilot board
was the cause. Double check by measuring pin 8 & 9 again. If it’s zero V. now, the Pilot board is defective. If
D11 is still on or pin 8 & 9 voltage still high check the Relay board.